Vascular occluders have been known for a number of years. Many types are in the form of a device which is implanted within a vessel of the patient and which has a structure which closes off the vessel so as to occlude blood flow. Occluders of this nature, sometimes referred to as vascular plugs, are preferable over more traditional forms of occluder, such as vascular constrictors, which generally require an invasive medical procedure. Vascular occluders, on the other hand, can be deployed endoluminally in a significantly faster and less traumatic medical procedure.
Vascular occluders may be designed or used to provide temporary occlusion, for example to be effective only for the duration of a medical procedure or during a period of treatment. Occlusion may also be permanent, in which case the occluder will be left within the patient indefinitely.
There are generally two types of vascular occluders. The first type promotes embolization within the vessel, for instance by slowing the flow of blood through the device and in some cases with the addition of embolization promoters. Such devices do not produce immediate occlusion of the vessel as they rely upon the formation of sufficient blood clotting to act as the occluding barrier. Sufficient thrombosis can take hours, days or even weeks in some instances.
Another type of vascular occluder has an impervious element, typically a membrane, attached to a supporting structure which gives it a conical shape. The wide end of the device expands to spread across the entire diameter of the vessel and thus creates an instantaneous barrier to blood flow. Other examples provide an inflatable balloon or chamber, which is filled with fluid to expand the balloon or chamber and thereby cause it to fill the diameter of the vessel in which the balloon or chamber is placed, thereby closing off the vessel. In many cases immediate occlusion of this type is preferable. However, some designs of such occluders do not reliably counter the full force of the blood stream, leading to migration of the device, loss of positional orientation, failure to achieve a full seal against the vessel wall and thus failure of the device. Furthermore, some such devices can fail to deploy properly in the vessel, leading to them being ineffective from the start.
In addition to difficulties in accurate placement and risk of migration, an occluder may also leak or become dislodged if the vessel changes size or shape over time. Such size or shape change can lead to loss of connection to the vessel wall.
Some examples of known vascular occluders can be found in U.S. Pat. No. 6,638,293 and US-2008/0221600.